Fuel monitoring systems for aircraft typically use capacitive fuel-gauging sensors. These sensors determine the amount of fuel in a tank by measuring the pressure near the bottom of the tank relative to a measurement of pressure above the fuel-air interface, and determining the height of the fluid from the pressure differential. From the height of the fluid and knowledge of the tank geometry, the amount of fuel in the tank may be ascertained. The capacitive fuel-gauging sensors determine the differential pressure by deflecting a diaphragm or other deformable element, and measuring the deflection with a capacitive pickoff mechanism. Such sensing mechanisms typically require entry at one or more points in the fuel tank and associated tubing to access the pressure ports for pressure measurements, along with wiring or cabling that may be inside the fuel tank or along the fuel lines. Fuel quantity gauging systems with these relatively large and bulky transducers are heavy and require several connection points with the tank.
An improved fuel-monitoring system for an aircraft would eliminate the need, for pressure sensors and their associated pressure ports, and would have minimal or no contact with the fuel. It would be less susceptible to electromagnetic interference (EMI), and could also detect damage to the fuel tank or to the fuel-gauging system. The fuel-tank gauging system would benefit from a fuel-height or fuel-level measurement system that is small, compact and light, resulting in considerable weight and space savings.
It is desirable to provide an integrated fuel-tank system that overcomes the deficiencies and obstacles of capacitive fuel-gauging sensors for monitoring fuel levels in fuel tanks.